Breast cancer is a complex disease with significant effects world-wide. There are multiple factors associated with its development, including a well-defined preneoplastic stage and a correlation with the amount of dietary fat. However, cellular events which establish the disease prior to the emergence of obvious tumors, and the effects of tumor promoters on that emergence, are completely obscure. We will use a combination of in vitro and in vivo approaches to analyze the effect(s) of a polyunsaturated fatty acid (PUFA) diet on chemical carcinogen-induced mammary tumorigenesis in the classical murine model. We will determine whether PUFA promotion enhances DMBA-induced tumorigenesis and/or preneoplasias in BALB/c mice. Mammary tissue will be dissociated and epithelial cells cultured in collagen gells. Several in vitro assays will be employed to detect and characterize cells with preneoplastic or transformed phenotypes in chemical carcinogentreated mammary epithlia; the effect of PUFA promotion on the number and phenotypic properties of such altered cells will be determined. Transplantation of selected cells into cleared mammary fatpads will provide in vivo correlates of in vitro asays. We will determine the effect of promoters on the expression of cellular genes (53K cellular protein, endogemmous MMTV) which may be involved in neoplastic progression in the mammary sytem. We will attempt to develop and in vitro system which duplicates early events in mammary tumorigenesis in order to identify and evaluate the effects of putative promoters. The kinetics of appearance and phenotypic characteristics of altered cells generated during latent periods of tumors induced by chemical carcinogen in the presence of various promotion regimensw ill be established. The proposed studies will recorgnize the effects of tumor promoters ont the progression from normal to preneoplastic to tumor cell phenotypes in mammary tissue, may yield a rapid assay for tumor promoters in the mammary system, and may provide a rational basis for new methods of early detection, prevention, or therapy in breast cancer.